Middle doctrine

'Many were tempted by the idea,' [St.] Mark [of Ephesus] continued, 'that one can find a medium between two doctrines. True: one can find such expressions which, having a double meaning, could at the same time express something between the two doctrines. But a doctrine midway between two contrary doctrines on the same subject is impossible; for in this case it must be something between truth and falsehood, between an affirmation and a negation. Thus, if the Latin doctrine of the Spirit’s procession from the Son is just, then ours is false. What middle doctrine can there be here?'